Stencil duplicating inks



United States Patent STENCIL DUPLICATING INKS Thomas Seal Chambers, Chicago, Robert Thompson Florence, Park Ridge, 111., assignors to A. B. Dick Company, Niles, 111., a corporation of Illinois No Drawing. Application March 27, 1952, Serial No. 278,947

4 Claims. Cl. 106-24) This invention relates to w'ater-tbase stencil duplicating inks adapted for use with stencil duplicating machines or for use in other stencilling operations where ink is transferred through stencil openings to an impression medium.

This application is a continuation-in-part of our copending application, Serial No. 93,414, filed May 14, 1949, and now abandoned.

In a stencil duplicating machine of the rotary type or the like, ink is supplied in continuous fashion to an ink pad or other like reservoir or distributing medium. After uniform distribution therein, the ink is transferred through the opening of a stencil to the impression medium, chiefly in response to forces developed at the point of contact between a rotating cylinder and the impression roller. For the most part, drying of the applied ink occurs by absorption of the vehicle or carrier into a portion of the impression medium or into the interstices between the fibers of which the impression medium is formed.

The characteristics desirable in a stencil duplicating ink are manifold and in many respects non-analogous to ink compositions commonly used for printing or for writing. For example, in order to function properly in the duplieating machine, the ink should have sufiicient body to minimize leakage from the cylinder and the ink pad and to prevent flooding of the stencil. On the other hand, in order to produce uniform and good copy, the ink should have sufiicient flow to effect satisfactory transmission through the stencil to the impression medium and to enable uniform and rapid distribution of the ink through the ink pad. The ink should be suificiently slow drying in the machine to minimize premature hardening on the ink pad or undesirable clogging of the stencil openings. At the same time, the ink should be quick drying when applied to the impression medium, otherwise it is necessary to resort to special devices or other costly practices in order to handle copy within a reasonable time and to eliminate setoff. The ink should dry without feathering, without forming an oily or colored letter outline, refer-red to by the industry as halo, and it should not be subject to show-through, which may be defined as visibility from the opposite side of the impression medium. The ink should also be stable and non-corrosive to the machine parts with which it might come in contact. Upon drying, it should be resistant to moisture, the common solvents and other substances with which the copy might come in contact a an incidence to normaluse.

Many of these characteristics are wholly lacking in stencil duplicating inks that have heretofore been pro duced. Preparation of an acceptable stencil duplicating ink has, in the past, been limited because of the presence of large amounts of oil, deemed necessary to provide for flow of the desired character and to function simultaneously as the carrier for the coloring agent. The. greater proportion of oils which have been used are selected of the non-drying type such as castor oil, palm oil, and cocoan'u t oil;

When such oils, which are non-drying in character, are

used in large amounts,,they permit a highly objectionable degree of setotf and smear unless special devices are used in the handling of the copy. The commonest device to cope with this problem is the costly and awkward practice of slip-sheeting, that is, the insertion of interlayer sheets between successive copies as they are duplicated. The problem may be alleviated, to a limited extent, by using as the impression medium highly absorbent paper stock whichrapidly distributes the vehicle, but the use of such absorbent medium makes it practically impossible to obtain sharply-defined. copy because of feathering of the ink.

The high oil content is directly responsible for the presence of objectionable letter outlines or halo in copy prepared 'with oil base inks. Stencil duplication with oil- 'base ink is burdened further by the fact that its use is limited to impression media of a highly absorbent nature and cannot be used successfully with hard or highly filled paper such as card, ledger, bond, or enamel stock.

Oil-base emulsion inks constituted with less oil have been formulated to relieve some of the objectionable features of the non-emulsion inks, but many of the limitations inherent in the oil still remain. Emulsion inks which have heretofore been produced present other operating problems because they are characterized by lower stability and separation often occurs at some stage in its use prior to transmission through the stencil, whereby the ink pad or the stencil, orboth, may become clogged to prevent uniform ink distribution and complicate the production of good copy. In addition, the inner phase of the ink emulsion frequently contains sulfonated glycerides, which are corrosive to the machine part or other elements with which the ink might be associated.

It is an object of this invention to produce a stencil duplicating ink which contains a desired balance in characteristics of thetype previously described.

Another object is to produce a stencil duplicating ink that is substantially free of oil and is thereby not limited to the restrictions imposed by the use of oily substances.

A further object is to produce a stencil duplicating ink having flow of the desired character in proper balance to operate successfully in stencil duplicating machines and other processes in the production of copy of good quality. A still further object is to produce an oil free stencil duplicating ink which has the desired balance of slow drying while in the stencil duplicating machine and quick drying upon transmission to the impression medium.

A still further object is to produce a stencil duplicating ink which may be used for the production of copy on hard, filled, or highly finished impression media without slip-sheeting or the use of other costly and undesirable devices.

Another-object is to produce a stencil duplicating ink which is quick drying so as to permit handling of the copy almost immediately after duplication without setofi or smear, and which, upon drying, becomes substantially impervious to moisture, many hydrocarbons and solvents with which the copy might come in contact.

A further object is to produce a stencil duplicating ink which is not subject to the objectionable features of ink compositions which have heretofore been produced and which is capable of meeting substantially all of the characteristics desired in a good stencil duplicating ink.

A still further object is to produce a low viscosity stencil duplicating ink having flow of the desired character and which is substantially non-corrosive, non-inflammable, stable, safe and easy to manufacture and use.

A very important object of this invention is to formulate a stencil duplicating ink without the use of oil. This we have succeeded in accomplishing by the production of a water-base stencil duplicating ink having characteristics that surpass ink compositions which have heretofore been developed. The term water base may be used to define inks prepared in accordance with our invention because water is present as the major diluent and carrier and is used to dissolve the bodying agents which impart flow of the desired character. In the practice of this invention, the water content of the ink composition may be as high as 75 to 85% by weight of the composition.

Water-base stencil duplicating inks embodying features of our invention are characterized by having a measurable viscosity which is much lower than the viscosity of oilbase inks or oil-emulsion inks operable under corresponding conditions. Viscosity can be used as a measure for certain flow characteristics, yet we find it impractical presently to define the desired flow characteristics rigidly and exclusively in the terms of viscosity. When measured by a Stormer Viscosimeter using a standard cup with a thermometer well and with a center bafile and while operating under a ZOO-gram load at 20 C., water-base inks embodying features of this invention provide a reading between 35 to 150 seconds. Suitable oil-base inks have a reading between 800 and 1000 seconds, and many oilemulsion inks have a reading between 650 and 800 seconds. The lower viscosity permissible with water-base inks of the type produced by this invention favors more rapid and uniform distribution of the ink throughout the ink pad and greater ease of transmission and operation in the duplicating process.

Bodying and fiow of the desired character in the stencil duplicating ink composition may be derived by the solution of a protein such as gelatin, zein, casein, animal glue, and the like. The salts of the proteins may also be used in the practice of this invention, such as ammonium caseinate, sodium caseinate, and the like. In order to secure body of the desired character in the ink com position, such proteins may be present in amounts ranging from 3 to by weight of the ink composition, depending upon the character thereof and the ingredients in the ink composition with which it is associated. For example, 6% by weight casein may be sufiicient in the presence of an alkalizing base such as an alkali metal base or salt or ammonium hydroxide while lesser amounts in the range of 3 to 4% may be sufficient in the absence thereof. It is preferred to make use of gelatin in amounts ranging from 2 to 5% by weight in the ink composition. The viscosity range is not to be taken as a strict limitation for defining the concentration of the bodying agent to be used therein, because the flow requirements for the ink composition changes in accordance with modifications in duplicating machines and in the practices of their use. Therefore, it will be understood that changes in amounts of such bodying agents may be made in accordance therewith without departing from the spirit of the invention.

As coloring agent, dyes or pigments, soluble or dispersible in aqueous medium may be used. Representative of the class of dyes having the desired solubility characteristics are the nigrosine dyes, triphenylmethane dyes, rhodamine dyes, thioflavine dyes, auramine dyes, quinonimide dyes, xanthane dyes, sulphonated triphenylmethane dyes, and nitro dyes. These include acid dyes such as the mono-, di-, and tri-sodium sulphonates of the nitro, azo. pyrazoline, quinoline, azine, xanthane, and anthraquiuone groups. Suitable pigments include lamp black, zinc oxide, titanium oxides, malachite green, iron blue, cadmium yellow, and the like. When pigments are used, they are usually dispersed as the discontinuous phase in suitable carriers such as water, solutions of resin, and the like.

The amount of dye in any formulation depends upon the characteristics of the coloring material. Some dyes, even when used in small quantities, are capable of imparting sutficient color to lend legibility to the copy. With others, it is necessary to use higher concentrations of dye to secure the desired effect. The lower limit of dye concentration is determined by its tinctorial strength, which may vary widely from compound to compound. The upper limit is often influenced by solubility factors or by the effect of the dye on other ingredients of the ink composition. We have found that water-soluble nigrosine dyes in amounts ranging from 3 to 7% by weight are suitable for water-base stencil duplicating inks. Other dyes may be used in corresponding ratio in accordance with their characteristics as pointed out above. When pigments are used, it is often desirable to use concentrations higher than 3% by weight, with the upper limit being in the range of about 15% by weight or more in some instances.

in order to increase the penetrabil-ity of the duplicating ink into the impression medium, and in order to improve the characteristics of the ink with respect to its distribution through the ink pad of the stencil, it is desirable to incorporate a wetting agent as an ingredient in the composition. A suitable wetting agent may be selected from well-known materials such as the dioctyl esters of sodium sulfosuecinates (Aerosols), quaternary ammonium salts in which one of the organic groups is a fatty acid of higher carbon length (Duponols), dibutylphenol sodium disulfonates (Areskelene), sulfonated ethers (Tensol), or the like. Less than 2%, but more than 0.2%, by weight of wetting agent is ordinarily sufficient to impart the desired wetting characteristics, although more may be used, if desired.

Another important modification in stencil duplicating compositions embodying features of this invention comprises the addition of a humectant which operates to reduce the rate of evaporation of the diluent. More important, the humectant appears in some instances to be capable of modifying theapparent flow properties of the ink composition. Such modification is not necessarily measurable by viscosimeters operating at high shear, but exists in fact to the extent that leakage from the ink pad is greatly minimized and operation of the duplicating machine substantially simplified. Under high shear, such as the forces operating While the ink is being forced through the stencil during duplication, the modified flow properties are not apparent, and, therefore, the ink flows as a liquid apparently having little additional viscosity. Liquid polyhydric alcohols, such as ethylene glycol, diethylene glycol, glycerine, and polyglycols, appear to impart these characteristics. Use may also be made of alkylolamine such as diethanolamine, triethanolamine sulfamate, monoisopropanolamine sulfamate, and the like. In specific application, from 10 to 40% by weight of the polyhydric alcohols may be used as an ingredient of the ink composition.

Inmost instances, greater insolubilization of the proteins upon drying may be achieved by the use of an aldehyde latent while in aqueous solution but which becomes reactive upon drying to insolubilize the bodying agents whereby they become more effective as a resistant adherent base for protecting the copying. Representative of such aldehydes are materials of the type glyoxal and pyruvic aldehyde. Glyoxal may be used in amounts of 5% by weight of the ink composition or in amounts of about 5 to 20% by weight of the bodying substance. Larger amounts of pyruvic aldehyde may be required, such as up to 10% by weight of the ink composition to give corresponding results.

When insolubilization by reaction with a latent aldehyde is possible, it is preferred to use a polyhydric alcohol and the latent insolubilizing agent in combination in the same formulation. When s'o combined, the aldehyde is able also to react with the polyhydric alcohol as well as with the bodying material when constituted with hydroxyl or amino groups. The reaction is in the nature of a condensation to form corresponding acet-als, hemiacetals and crosslinked polymers. I

Without limiting our invention to any particular composition, the following examples will serve to illustrate suitable stencil duplicating inks embodying f atures of our invent on: i 5i Exampled Percentage Calcocid Scarlet MOO (water-soluble dye). Dioetylester of sodium sulio ucpinste (wet fnkagent). Glyoxal. Gelatin.

Ethylene glycol. Water.

Urea.

Example Material I Nigrosine J (water soluble dye) Blood albumin. Water.

Example 3 Material Soya protein.

Triethanolamine.

Aquablak in aqueous dispersion. Water.

Wetting agent.

Example 4 Material Calcocid Scarlet M OO (water soluble dye). Dioctylester of sodium sulfosuccinate (50% solids). Glyoxal (30% in water solution). Ethylene glycol.

Gelatin (3% solution in water).

Example 5 Material Aquablak in aqueous dispersion. Wetting agent (50% solids). Borax.

Ammonium hydroxide.

Casein.

Water.

Example 6 Material Calcocid Scarlet MOO (water soluble dye). gioctylester of sodium suliosuccinate (wetting agent).

orax. Ammonium hydroxide.

HHHHHQ 1n. Ethylene glycol. Water.

Example 7 Material Nigrosine. Wetting agent. G}yoxal (30% solution).

ue. Ethylene glycol. Water.

employed, it may be incorporatedinto the formulation withsufl'icient stirring'to distribute the dispersed pigment particles-uniformly throughout the ink composition.

By the use of these new and improved stencil duplicating inks, drying has been found to take place at a speed which is beyond that heretofore contemplated for stencil duplicating inks of the oil base type thus making -it possible'to-handle copy almost immediately. -It is possible to eliminate set-oif without the costly and cumbersome technique of slip-sheeting. i i

It has also been found possible to producecopy on hard stock and highly finished impression medium while still being able to handle the work substantially immediately after duplication. The inks produced by this invention have been found to dryrapidly on'bond, ledger, card or enamel stock, impression media which have heretofore not been suitable for general use with stencil duplicating machines.

The materials present in stencil duplicating ink compositions of the type described are incapable of producing an undesirable show-through or halo because the possible ingredients such as water or other diluent are substantially completely eliminated from the impression medium upon drying and are not resident as are the oils of duplicating inks which have heretofore been produced.

It will be evident that a number of other important advantages are derived from the use of water base stencil duplicating inks of the type produced herein. These include the elimination of possible separation of the ingreclients of the ink composition either in use or prior to use because of instabilities which might ordinarily have developed; simplification in the processes of cleaning a machine and stencil as by the use of a simple water rinse because the ink composition before drying remains readily soluble in water and any of the common solvents; selfsealing characteristics derived from the use of the polyhydric alcohol or the protein bodying agent alone or in combination; viscosity and flow properties so related to rate of shear that inadvertent flow in the ink cylinder is substantially eliminated without reducing the ability of the ink composition to pass through the stencil openings in normal duplicating operations; and simplicity in the manufacture of the ink compositions responsive chiefly to the use of Water soluble elements as ingredients and the possible elimination of grinding or other means for incorporating the colors into the ink composition.

It will be understood thatthe basic substances may be prepared with a minimum amount of water incorporated therein for marketing in concentrated form as a paste or without water incorporated therein for marketing in dry form for subsequent dilution at the station of use with aqueous medium to the desired viscosity. It will be further understood that miscible solvents, such as the lower alcohols may be substituted in part for water as the diluent in the ink composition. Numerous other modifications and substitutions may be made with respect to the materials and amounts and method of incorporation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. A stencil duplicating ink consisting essentially of more than 50 percent by weight of water as the principal diluent, from 3-15 percent by weight of a tinctorial agent, from 3-15 percent by weight of a protein dissolved in the aqueous medium to body the ink composition and to provide an adherent base upon drying, a liquid polyhydric alcohol present in an amount up to 40 percent by weight, 0.2-2 percent by weight of a wetting agent, and an alde hyde selected from the group consisting of glyoxal and pyruvic aldehyde present in amounts ranging from 5-20 percent by weight of the bodying agent.

2. A stencil duplicating ink consisting essentially of 50 percent by weight water as theprincipal diluent, 3-15 percent by weight of a tinctorial agent, from 3-15 percent by weight of a protein dissolved in aqueous medium to body the ink composition and to provide an adherent base upon drying, a liquid polyhydric alcohol presentvin an amount up to 40 percent by weight, and an aldehyde selected from the group consisting of glyoxal and pyruvic aldehyde present in amounts ranging from 5-20 percent by weight of the bodying agent.

3. A stencil duplicating ink consisting essentially of more than 50 percent by weight water as the principal diluent, 3 15 percent by weight of a tinctorial agent, 3-15 percent by weight of a protein dissolved in aqueous medium to body the ink composition and to provide an adherent base upon drying, a liquid polyhydric alcohol present in an amount up to 40 percent by weight, and 0.2-2.0 percent by weight of a wetting agent. 4

- 4. A stencil duplicating ink consisting essentially of more than 50 percent by weight water as the principal diluent, 3-15 percent by weight of a tinctorial agent, 3-15 percent byweight of a protein dissolved in aqueous medium to body the ink composition and to provide an adherent base upon drying and a liquid polyhydric alcohol present in an amount up to 40 percent by weight.

ReferencesCited in the file of this patent UNITED STATES PATENTS 

1. A STENCIL DUPLICATING INK CONSISTING ESSENTIALLY OF MORE THAN 50 PERCENT BY WEIGHT OF A TINCTORIAL AGENT, DILUENT, FROM 3-15 PERCENT BY WEIGHT OF A TINCTORIAL AGENT, FROM 3-15 PERCENT BY WEIGHT OF A PROTEIN DISSOLVED IN THE AQUEOUS MEDIUM TO BODY THE INK COMPOSITION AND TO PROVIDE AN ADHERENT BASE UPON DRYING, A LIQUID POLYHYDRIC ALCOHOL PRESENT IN AN AMOUNT UP TO 40 PERCENT BY WEIGHT, 0.2-2 PERCENT BY WEIGHT OF A WETTING AGENT, AND AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF GLYOXAL AND PYRUVIC ALDEHYDE PRESENT IN AMOUNTS RANGING FROM 5-20 PERCENT BY WEIGHT OF THE BODYING AGENT. 